A Model of Cerebrovascular Reactivity Including the Circle of Willis and Cortical Anastomoses

Cerebrovascular pathologies are extremely complex, due to the multitude of factors acting simultaneously on cerebral hemodynamics. In this work, a mathematical model of cerebral hemodynamics and intracranial pressure (ICP) dynamics, developed in previous years, is extended to account for heterogeneity in cerebral blood flow. The model includes the Circle of Willis, six regional districts independently regulated by autoregulation and CO₂ reactivity, distal cortical anastomoses, venous circulation, the cerebrospinal fluid circulation, and the ICP–volume relationship. Results agree with data in the literature and highlight the existence of a monotonic relationship between transient hyperemic response and the autoregulation gain. During unilateral internal carotid artery stenosis, local blood flow regulation is progressively lost in the ipsilateral territory with the presence of a steal phenomenon, while the anterior communicating artery plays the major role to redistribute the available blood flow. Conversely, distal collateral circulation plays a major role during unilateral occlusion of the middle cerebral artery. In conclusion, the model is able to reproduce several different pathological conditions characterized by heterogeneity in cerebrovascular hemodynamics and cannot only explain generalized results in terms of physiological mechanisms involved, but also, by individualizing parameters, may represent a valuable tool to help with difficult clinical decisions.     

Role of tissue hypoxia in cerebrovascular regulation: a mathematical modeling study

This paper presents a mathematical model of cerebrovascular regulation, in which emphasis is given to the role of tissue hypoxia on cerebral blood flow (CBF). In the model, three different mechanisms are assumed to work on smooth muscle tension at the level of large and small pial arteries: CO₂reactivity, tissue hypoxia, and a third mechanism necessary to provide good reproduction of autoregulation to cerebral perfusion pressure (CPP) changes. Using a single set of parameters for the mechanism gains, assigned via a best fitting procedure, the model is able to reproduce the pattern of pial artery caliber and CBF under a large variety of physiological stimuli, either acting separately (hypoxia, CPP changes, CO₂ pressure changes) or in combination (hypercapnia+hypoxia; hypercapnia+hypotension). Furthermore, the model can explain the increase in CBF and the vasoconstriction of small pial arteries observed experimentally during hemodilution, ascribing it to the decrease in blood viscosity and to the antagonistic action of the flow-dependent mechanism (responsible for vasoconstriction) and of hypoxia (responsible for vasodilation). Finally, the interaction between hypoxia and intracranial pressure (ICP) has been analyzed. This interaction turns out quite complex, leading to different ICP time patterns depending on the status of the cerebrospinal fluid outflow pathways and of intracranial compliance. © 2001 Biomedical Engineering Society. PAC01: 8719Uv, 8719Tt, 8719Ff, 8380Lz     

Timing dependence of peripheral pulse‐wave‐triggered pulsed arterial spin labeling

Arterial spin labeling (ASL) has been developed into a useful technique that is capable of quantifying noninvasively local cerebral blood flow (CBF) using the water molecules in arterial blood as diffusible tracers. Pulsed ASL (PASL) is more strongly affected than continuous ASL (CASL) by cardiac pulsation, because the tag bolus is shorter than the cardiac cycle in most cases. No reports have yet clarified the effects of multiple cardiac phases on the quantification of CBF in PASL when triggering is used. Fourteen subjects participated in this study. Peripheral pulse‐wave‐triggered (PPWT)‐ASL was performed at various time points at the carotid artery (delay 0 ms, second point, foot, peak and tail) and compared with nontriggered (NT)‐ASL. Regions of interest (ROIs) were applied based on the anterior, middle and posterior cerebral artery (ACA, MCA, PCA) territories, and CBFs were compared among different time points and ROIs. PPWT‐ASL strongly affects CBF values compared with NT‐ASL in ACA and MCA territories, especially when measured at the foot of the carotid artery flow phase. CBF_NT was assumed to lie approximately between the minimum and maximum CBFs, with clear statistical significance in several ROIs at several time points of PPWT‐ASL, and CBF_NT was assumed to resemble ‘randomly triggered’ PPWT‐ASL. In conclusion, PPWT‐ASL strongly affects CBF values compared with NT‐ASL, particularly at the foot of the carotid artery flow in ACA and MCA territories. Copyright © 2013 John Wiley & Sons, Ltd.     

The critical closing pressure of the cerebral circulation

The critical closing pressure (CrCP) of the cerebral circulation indicates the value of arterial blood pressure (ABP) at which cerebral blood flow (CBF) approaches zero. Measurements in animals and in humans, have shown that the CrCP is significantly greater than zero. A simple mathematical model, incorporating the effects of arterial elasticity and active wall tension, shows that CrCP can be influenced by several structural and physiological parameters, notably intracranial pressure (ICP) and active wall tension. Due to the non-linear shape of the complete ABP-CBF curve, most methods proposed for estimation of CrCP can only represent the linear range of the pressure-flow (or velocity) relationship. As a consequence, only estimates of apparent CrCP can be obtained, and these tend to be significantly higher than the true CrCP. Estimates of apparent CrCP have been shown to be influenced by arterial PCO2, ICP, cerebral autoregulation, intra-thoracic pressure, and mean ABP. There is a lack of investigation, under well-controlled conditions, to assess whether CrCP is altered in disease states. Studies of the cerebral circulation need to take CrCP into account, to obtain more accurate estimates of cerebrovascular resistance changes, and to reflect the correct dynamic relationship between instantaneous ABP and CBF.     

Cardiac specific transcription factor Csx/Nkx2.5 regulates transient-outward K+ channel expression in pluripotent P19 cell-derived cardiomyocytes

We hypothesized that cerebral blood flow (CBF) regulation in the posterior circulation differs from that of the anterior circulation during a cold pressor test (CPT) and is accompanied by elevations in arterial blood pressure (ABP) and sympathetic nervous activity (SNA). To test this, dynamic cerebral autoregulation (dCA) in the middle and posterior cerebral arteries (MCA and PCA) were measured at three different conditions: control, early phase of the CPT, and the late phase of the CPT. The dCA was examined using a thigh cuff occlusion and release technique. The MCA and PCA blood velocities were unchanged at CPT compared with the control conditions despite an elevation in the ABP. The dCA in both the MCA and PCA remained unaltered at CPT. These findings suggest that CPT-induced elevations in the ABP and SNA did not cause changes in the CBF regulation in the posterior circulation compared with the anterior circulation.

     

Model-based noninvasive estimation of intracranial pressure from cerebral blood flow velocity and arterial pressure

Intracranial pressure (ICP) is affected in many neurological conditions. Clinical measurement of pressure on the brain currently requires placing a probe in the cerebrospinal fluid compartment, the brain tissue, or other intracranial space. This invasiveness limits the measurement to critically ill patients. Because ICP is also clinically important in conditions ranging from brain tumors and hydrocephalus to concussions, noninvasive determination of ICP would be desirable. Our model-based approach to continuous estimation and tracking of ICP uses routinely obtainable time-synchronized, noninvasive (or minimally invasive) measurements of peripheral arterial blood pressure and blood flow velocity in the middle cerebral artery (MCA), both at intra-heartbeat resolution. A physiological model of cerebrovascular dynamics provides mathematical constraints that relate the measured waveforms to ICP. Our algorithm produces patient-specific ICP estimates with no calibration or training. Using 35 hours of data from 37 patients with traumatic brain injury, we generated ICP estimates on 2665 nonoverlapping 60-beat data windows. Referenced against concurrently recorded invasive parenchymal ICP that varied over 100 millimeters of mercury (mmHg) across all records, our estimates achieved a mean error (bias) of 1.6 mmHg and SD of error (SDE) of 7.6 mmHg. For the 1673 data windows over 22 hours in which blood flow velocity recordings were available from both the left and the right MCA, averaging the resulting bilateral ICP estimates reduced the bias to 1.5 mmHg and SDE to 5.9 mmHg. This accuracy is already comparable to that of some invasive ICP measurement methods in current clinical use.     

Structural MRI of carotid artery atherosclerotic lesion burden and characterization of hemispheric cerebral blood flow before and after carotid endarterectomy

Collateral circulation plays a major role in maintaining cerebral blood flow (CBF) in patients with internal carotid artery (ICA) stenosis. CBF can remain normal despite severe ICA stenosis, making the benefit of carotid endarterectomy (CEA) or stenting difficult to assess. Before and after surgery, we assessed CBF supplied through the ipsilateral (stenotic) or contralateral ICA individually with a novel hemisphere-selective arterial spin-labeling (ASL) perfusion MR technique. We further explored the relationship between CBF and ICA obstruction ratio (OR) acquired with a multislice black-blood imaging sequence. For patients with unilateral ICA stenosis (n = 19), conventional bilateral labeling did not reveal interhemispheric differences. With unilateral labeling, CBF in the middle cerebral artery (MCA) territory on the surgical side from the ipsilateral supply (53.7 +/- 3.3 ml/100 g/min) was lower than CBF in the contralateral MCA territory from the contralateral supply (58.5 +/- 2.7 ml/100 g/min), although not statistically significant (p = 0.09). The ipsilateral MCA territory received significant (p = 0.02) contralateral supply (7.0 +/- 2.7 ml/100 g/min), while ipsilateral supply to the contralateral side was not reciprocated. After surgery (n = 11), ipsilateral supply to the MCA territory increased from 57.3 +/- 5.7 to 67.3 +/- 5.4 ml/100 g/min (p = 0.03), and contralateral supply to the ipsilateral MCA territory decreased. The best predictor of increased CBF on the side of surgery was normalized presurgical ipsilateral supply (r(2) = 0.62, p = 0.004). OR was less predictive of change, although the change in normalized contralateral supply was negatively correlated with OR(excess) (=OR(ipsilateral) - OR(contralateral)) (r(2) = 0.58, p = 0.006). The results demonstrate the effect of carotid artery stenosis on blood supply to the cerebral hemispheres, as well as the relative role of collateral pathways before surgery and redistribution of blood flow through these pathways after surgery. Unilateral ASL may better predict hemodynamic surgical outcome (measured by improved perfusion) than ICA OR.     

Cerebral vasospasm

Cerebral vasospasm (specifically, intracranial arterial spasm) is variously defined as: (1) an arteriographically evident narrowing of the lumen of one or more of the major intracranial arteries at the base of the brain due to contraction of the smooth muscle within the arterial wall, or due to the morphological changes in the arterial wall and along its endothelial surface that occur in response to vessel injury; (2) the delayed onset of a neurological deficit following subarachnoid hemorrhage, thought to be due to ischemia or infarction of a portion of the brain; or (3) the combination of these two features (symptomatic vasospasm). The arterial contraction of intracranial arterial spasm typically develops a few days after the rupture of an intracranial aneurysm and lasts 2 to 3 weeks. Such arterial spasm can also occur in other conditions such as head trauma. If it is severe enough it can lead to cerebral infarction. The pathogenesis of this condition is still unclear. Many ingenious attempts have been made to prevent or treat cerebral vasospasm, but most have failed. The best current approach is to ensure adequate blood volume, and to elevate the patient's blood pressure (especially if the aneurysm has been secured by an early operation). The continuing investigation of drugs such as calcium channel blocking agents to improve the cerebral circulation has begun to provide additional help.     

Computational Analysis of the Effects of Exercise on Hemodynamics in the Carotid Bifurcation

The important influence of hemodynamic factors in the initiation and progression of arterial disease has led to numerous studies to computationally simulate blood flow at sites of disease and examine potential correlative factors. This study considers the differences in hemodynamics produced by varying heart rate in a fully coupled fluid-structure three-dimensional finite element model of a carotid bifurcation. Two cases with a 50% increase in heart rate are considered: one in which peripheral resistance is uniformly reduced to maintain constant mean arterial pressure, resulting in an increase in mean flow, and a second in which cerebral vascular resistance is held constant so that mean carotid artery flow is nearly unchanged. Results show that, with increased flow rate, the flow patterns are relatively unchanged, but the magnitudes of mean and instantaneous wall shear stress are increased roughly in proportion to the flow rate, except at the time of minimum flow (and maximum flow separation) when shear stress in the carotid bulb is increased in magnitude more than threefold. When cerebral peripheral resistance is held constant, the differences are much smaller, except again at end diastole. Maximum wall shear stress temporal gradient is elevated in both cases with elevated heart rate. Changes in oscillatory shear index are minimal. These findings suggest that changes in the local hemodynamics due to mild exercise may be relatively small in the carotid artery. © 2003 Biomedical Engineering Society. PAC2003: 8719Uv, 8719Rr, 8380Lz     

Arterial and Venous Brain Reactivity in the Acute Period of Cerebral Concussion

Transcranial color duplex scanning of the cerebral vessels was used to study arterial and venous reactivity in 38 patients in the acute period of cerebral concussion (CC) and in 32 healthy volunteers. Arterial flow was assessed in the middle cerebral artery (MCA) and venous drainage in the basal vein of Rosenthal (BV). Cerebrovascular reactivity was assessed using hypercapnic and orthostatic tests. These studies showed that CC was not accompanied by marked changes in cerebral hemodynamics in the state of rest. During the acute phase of CC, about 20% of patients showed increases in peak blood flow velocity in the MCA, typical of cerebral hyperperfusion. Increases in the peak blood flow velocity in the BV were seen in 25% of patients with CC, compensating for impaired drainage via the superficial cerebral system. In normal subjects, cerebral venous reactivity to hypercapnia was greater than arterial reactivity, while reactivity to orthostasis corresponded to the magnitudes of arterial changes. The absence of quantitative differences in the responses of arterial and venous blood flow to hypercapnia and the predominance of venous reactivity to orthostasis in patients with CC indicates that these patients had impairments in the regulation of venous tone.     

脑电图空间对称指数与单侧大脑中动脉狭窄后侧支循环状态的相关性

目的：探讨脑电图空间对称指数（spatial hemispheric brain symmetry index, sBSI）与大脑中动脉（McA）狭窄后患者侧支循环代偿之间的关系。方法：对25例单侧MCA重度狭窄或闭塞的患者（病例组）和15例健康者（对照组）进行16导联脑电图常规检查,计算出脑电图sBSI。病例均为经脑血管造影术（DsA）证实为MCA狭窄或闭塞。再将病例组分为有明显侧支循环代偿组和无明显代偿组两组,观察脑电图sBSI与MCA狭窄或闭塞后有无侧支代偿的关系。结果：lO例MCA闭塞病变患者中8例有明显侧支代偿。15例MCA重度狭窄患者中5例具有明显侧支代偿。病例组sBSI（0．078±0．025）明显大于正常对照组sBSI（0．058±0．010）,P=0．004;有侧支代偿病例组的脑电图sBSI（0．068±0．009）明显小于无侧支的病例组sBSI（0．092±0．032）,P=0．011。结论：脑电图检查作为一项无创的检查方法,其sBSI在评估MCA狭窄或闭塞后侧支代偿状态有一定的可行性。     

Intracranial flow patterns at increasing intracranial pressure

Summary In the course of a pilot study, changes in intracranial pressure were compared with the transcranial Doppler findings of the middle cerebral artery. The cases of five patients were discussed who developed dissociated brain death in spite of intensive therapeutic measures. The studies showed that changes of the intracranial pressure influenced the flow patterns considerably: at increasing intracranial pressure (decreasing cerebral perfusion pressure) a progressive reduction of the systolic and above all diastolic flow velocities and finally a pendular flow occurred. These changes could be recorded quantitatively by means of the Pourcelot index and the mean flow velocity. Acute changes of the intracranial pressure can be detected at an early stage by noninvasive transcranial Doppler studies and can be followed by adequate intensive therapy.Abbreviations CPP Mean cerebral perfusion pressure - ICP Intracranial pressure - MAP Mean systemic arterial pressure - MCA Middle cerebral artery - MFV Mean flow velocity - pCO₂ Carbon dioxide tension - R Index de résistance=Pourcelot index - TCD Transcranial Doppler Supported by the DFG (SFB 330)     

Cerebral blood flow and metabolism during exercise

During exercise regional cerebral blood flow (rCBF), as blood velocity in major cerebral arteries and also blood flow in the internal carotid artery increase, suggesting an increase in blood flow to a large part of the brain. Such an increase in CBF is independent of the concomitant increase in blood pressure but is modified by the alteration in arterial carbon dioxide tension (PaCO(2)). Also, the increase in middle cerebral artery mean blood velocity (MCA V(mean)) reported with exercise appears to depend on the ability to increase cardiac output (CO), as demonstrated in response to beta-1 blockade and in patients with cardiac insufficiency or atrial fibrillation.Near-infrared spectroscopy (NIRS) determined cerebral oxygenation supports the alterations in MCA V(mean) during exercise. Equally, the observation that the cerebrovascular CO(2)-reactivity appears to be smaller in the standing than in the sitting and especially in the supine position could relate to the progressively smaller CO.In contrast, during exercise "global" cerebral blood flow (gCBF), as determined by the Kety-Schmidt technique is regarded as being constant. One limitation of the Kety-Schmidt method for measuring CBF is that blood flow in the two internal jugular veins depends on the origin of drainage and it has not been defined which internal jugular venous flow is evaluated. Such a consideration is equally relevant for an evaluation of cerebral metabolism during exercise.While the regional cerebral uptake of oxygen (O(2)) increases during exercise, the global value is regarded as being constant. Yet, during high intensity exercise lactate is taken up by the brain and its O(2) uptake also increases. Furthermore, in the initial minutes of recovery immediately following exercise, brain glucose and O(2) uptake are elevated and lactate uptake remains high.A maintained substrate uptake by the brain after exercise suggests a role for brain glycogen in cerebral activation, but the fate of brain substrate uptake has not yet been determined.     

血流动力学的医学应用与发展

血流动力学是指血液在血管系统中流动的力学,主要研究血流量、血流阻力、血压、切应力、扰动流等,以及它们之间的相互关系,对人类生命健康具有重要的影响。血流动力学在血管的弯曲、狭窄、堵塞、分叉以及肿瘤的治疗等方面具有重要的临床研究意义。目前,血流动力学在动脉血管搭桥、冠状动脉狭窄、腹主动脉瘤、动脉粥样硬化、脑动脉肿瘤以及旋动流等方面引起广泛研究。伴随着血流动力学的深入研究,心脑血管的手术规划、介入治疗等得到快速发展,基于血流动力学的临床检测和治疗仪器也越来越多。血流动力学因素,如血管压力、血管阻力、血流量、壁面切应力、血液黏度、流动分离、湍流、涡流等对常见血管疾病以及术后并发症的影响机理正在逐步深入探索之中,并已经取得了一定成果。     

Intramyocardial Influences on Blood Flow Distributions in the Myocardial Wall

Flow velocity wave forms of coronary arterial inflow and venous outflow of myocardium are influenced by cardiac contraction and relaxation: arterial flow is exclusively diastolic; venous outflow is systolic. We first discuss the intramyocardial microvascular flow dynamics, then present some results of visualization of transmural microvessels by our needle-probe charge coupled device (CCD) microscope, along with an interpretation of the arteriolar and venular hemodynamics through a cardiac cycle. After describing a hierarchical system of coronary microvessels (small artery, arteriole, and capillary), we emphasize the importance of spatial heterogeneity of blood supply to myocardium with reference to a minimal vascular control unit (400 m). An understanding of mechanoenergetic interaction is fundamentally important to an understanding of intramyocardial coronary circulation, and the Physiome Project will provide powerful tools for understanding the integrated role of the intramyocardial microcirculation system. © 2000 Biomedical Engineering Society. PAC00: 8719Hh, 8719Ff, 8719Tt     

实验性大鼠脑血管痉挛动物模型制备

目的探索实验性SD大鼠蛛网膜下隙出血（SAH）脑血管痉挛模型制备方法。方法尾动脉取血,立体定位仪下枕大池二次注血,印度墨水灌注测量大脑中动脉、颈内动脉和基底动脉直径,Morris水迷宫行为学测试,测定血中内皮素-1、一氧化氮合酶含量。结果 SAH组脑血管明显变细,Morris水迷宫显示有学习记忆能力减退,大脑中动脉、颈内动脉和基底动脉直径分别为（169.33±8.67）mm、（227.33±14.25）mm、（226.33±5.99）mm;内皮素-1和一氧化氮合酶分别为（214.36±10.49）g/L、（211.15±16.99）U/mL,与对照组比较有统计学差异。结论本实验方法能够制备蛛网膜下隙出血后脑血管痉挛模型。     

Cerebral perfusion characteristics show differences in younger versus older children with sickle cell anaemia: Results from a multiple‐inflow‐time arterial spin labelling study

Sickle cell anaemia (SCA) is associated with chronic anaemia and oxygen desaturation, which elevate cerebral blood flow (CBF) and increase the risk of neurocognitive complications. Arterial spin labelling (ASL) provides a methodology for measuring CBF non‐invasively; however, ASL techniques using only a single inflow time are not sufficient to fully characterize abnormal haemodynamic behaviour in SCA. This study investigated haemodynamic parameters from a multi‐inflow‐time ASL acquisition in younger (8–12 years) and older (13–18 years) children with SCA with and without silent cerebral infarction (SCI+/?) (n = 20 and 19 respectively, 6 and 4 SCI+ respectively) and healthy controls (n = 9 and 7 respectively). Compared with controls, CBF was elevated globally in both groups of patients. In the younger SCA patients, blood oxygen content was negatively correlated with CBF in the middle and posterior cerebral artery territories and significantly positively correlated with bolus arrival time (BAT) in the anterior and middle cerebral artery territories. In older children, SCA patients had significantly shorter BAT than healthy controls and there was a significant negative correlation between CBF and oxygen content only in the territory of the posterior cerebral artery, with a trend for a correlation in the anterior cerebral artery but no relationship for the middle cerebral artery territory. In the younger group, SCI+ patients had significantly higher CBF in the posterior cerebral artery territory (SCI+ mean = 92.78 ml/100 g/min; SCI? mean = 72.71 ml/100 g/min; F = 4.28, p = 0.04), but this no longer reached significance when two children with abnormal transcranial Doppler and one with haemoglobin SC disease were excluded, and there were no significant differences between patients with and without SCI in the older children. With age, there appears to be increasing disparity between patients and controls in terms of the relationship between CBF and oxygen content in the anterior circulation, potentially predicting the risk of acute and chronic compromise of brain tissue.     

颈动脉切除术的体会

目的:探讨颈动脉切除术的安全检测指标,确保手术成功和患者生命安全.方法:19例行颈动脉切除的肿瘤患者采用术前体外或体内颈动脉压迫训练法,阻断颈动脉血流,通过经颅多普勒(TCD)和数字减影(DSA)检测了解脑侧支循环建立及交通动脉开放情况.术中夹闭颈总动脉,TCD检测患侧大脑前动脉(ACA)和大脑中动脉(MCA)代偿情况.结果:体外压迫训练18～45 d,体内压迫训练7～9 d达到合格标准.18例肿瘤全切,1例肿瘤包绕椎动脉入颅处行部分切除.无死亡病例和术后脑缺血及偏瘫等严重并发症.16例随访1～5 a无复发.结论:缓慢渐进的颈动脉压迫训练是促进脑侧支循环建立和患侧脑血流代偿的有效方法.TCD和DSA检测对手术成功和保障患者生命安全起决定性作用.     

An Integrative Model of the Cardiovascular System Coupling Heart Cellular Mechanics with Arterial Network Hemodynamics

The current study proposes a model of the cardiovascular system that couples heart cell mechanics with arterial hemodynamics to examine the physiological role of arterial blood pressure (BP) in left ventricular hypertrophy (LVH). We developed a comprehensive multiphysics and multiscale cardiovascular model of the cardiovascular system that simulates physiological events, from membrane excitation and the contraction of a cardiac cell to heart mechanics and arterial blood hemodynamics. Using this model, we delineated the relationship between arterial BP or pulse wave velocity and LVH. Computed results were compared with existing clinical and experimental observations. To investigate the relationship between arterial hemodynamics and LVH, we performed a parametric study based on arterial wall stiffness, which was obtained in the model. Peak cellular stress of the left ventricle and systolic blood pressure (SBP) in the brachial and central arteries also increased; however, further increases were limited for higher arterial stiffness values. Interestingly, when we doubled the value of arterial stiffness from the baseline value, the percentage increase of SBP in the central artery was about 6.7% whereas that of the brachial artery was about 3.4%. It is suggested that SBP in the central artery is more critical for predicting LVH as compared with other blood pressure measurements.     

Real-time continuous neuromonitoring combines transcranial cerebral Doppler with near-infrared spectroscopy cerebral oxygen saturation during total aortic arch replacement procedure: a pilot study

The purpose of this investigation was to use combined transcranial cerebral Doppler (TCD) and near-infrared spectroscopy cerebral oxygen saturation (NIRS) during total aortic arch replacement (TAAR) to monitor middle cerebral artery blood flow velocity and regional cerebral oximetry (rSO(2)) changes to provide a clinical basis for protective measures that may decrease injury of the central nervous system. Consecutive 12 adult patients underwent deep hypothermic circulatory arrest (DHCA) and antegrade selective cerebral perfusion (ASCP) during TAAR. A TCD probe was placed at the temporal windows after induction of anesthesia and the NIRS probe placed on the forehead of patients to collect perioperative, intraoperative, and postoperative hemodynamic parameters, and cerebral blood flow (CBF) and rSO(2) during cardiopulmonary bypass (CPB). In this retrospective case series, all patients survived, and there were no postoperative neurologic complications. There was no significant correlation between the mean arterial pressure and rSO(2). The middle cerebral artery mean velocity (VmMCA) and rSO(2) were significantly correlated, and main pump flow significantly correlated with rSO(2). After ASCP, VmMCA, rSO(2), and venous oxygen saturation were significantly lower than before ASCP, but VmMCA and rSO(2) returned to pre-CPB levels postoperatively. After off pump, the flow of ASCP showed a significant positive correlation with VmMCA and rSO(2). During DHCA when ASCP flow was lower than 5 ml/kg/min, TCD could not detect the MCA blood flow signal. When the flow of ASCP was above keeping around 10 ml/kg/min, MCA CBF velocity was maintained and rSO(2) > 45%. The combination of TCD and NIRS can be effective in monitoring brain function during DHCA with ASCP and may provide a guide for decreasing brain injury during the TAAR procedure.